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Balsam Wooly Adelgid

Adelges piceae

The Balsam wooly agelid is very small, and has a covering of white wax-like threads. This agelid affects true firs in California and other western states.

Location: California, Oregon, Washington, Idaho, and British Columbia, BWA

Impact Significance: Damage Occurances

Hosts: Balsam woolly adelgid feeds predominantly on subalpine fir and grand fir.

Biology:  This adelgid is very small, 1mm or less in length, and relatively inconspicuous except for a covering of white wax-like threads that gives the insect its name. Two unique features of this adelgid: all are female, capable of starting a new infestation alone, and all are flightless.

Damage:  Heavy balsam woolly adelgid feeding modifies the bark and after a few years they can’t penetrate the thicker layers. Attractive feeding space on the tree diminishes and populations die out. If a tree survives the initial infestaton, mortality will likely be avoided.

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Cooley Spruce Gall Adelgid

Adelges cooleyi

More information coming soon

Gouty Pitch Midge

Cecidomyia piniiopsis

More information coming soon

Hemlock Woolly Adelgid

Adelges tsugae

Hemlock woolly adelgid (HWA), Adelges tsugae, is member of the Sternorrhyncha suborder of the Order Hemiptera. It feeds by sucking sap from hemlock and spruce trees.

Location: Oregon, California, Virginia, Delaware, Maryland, New York, Pennsylvania, New Jersey, Connecticut, Rhode Island, West Virginia, North Carolina, South Carolina, Georgia, Maine, Vermont, New Hampshire, Tennessee, and Kentucky

Impact Significance: Generally, this pest has not caused severe damage in the western United States. However, in much of Pennsylvania it has caused significant damage to eastern hemlock, Tsuga canadensis in ornamental plantings and the forest.

Hosts: Hemlock and spruce trees.

Biology: The hemlock woolly adelgid (HWA, Adelges tsugae) is an aphid-like, invasive insect.

Damage:  Moderate hemlock woolly adelgid populations may cause a reduction in tree health. Severe infestations may result in premature needle drop, reduced twig growth, dieback, or death of trees.

Pine Wood Nematode

Bursaphelenchus xylophilus

Status:  Uncertain, however thought to be native throughout North America


Hosts (in California):  Found in trees or logs of over 30 conifer species including Abies (fir), Pinus (pines), Cedrus (cedars), Larix (larch), Picea (spruce) and Pseudotsuga (Douglas-fir).  Most trees are resistant except when seriously water stressed.  Primarily exists as a problem in landscape plantings.  Main landscape trees impacted are exotic pines including Japanese black (P. thunbergii), Japanese red (P. densiflora), Scots (P. sylvestris) and Austrian (P. nigra) pines.


Management: No major management options exist for pine wood nematode.  Individually infected branches can be trimmed.  Infected landscape trees can be replaced with non-hosts or native species.


Highlights:  Nematodes are microscopic eel-like organisms.  The pine wood nematode lives within the cells of its host plants or within its insect vector.  Insects, primarily longhorn beetles in the genus Monochamus (wood boring long horn beetles), vector the nematodes when they attack dead or dying trees or when feeding or laying eggs on new hosts.  Within the tree the nematodes move first to the resin ducts and then to xylem cells.  Toxins produce cause the cells to break down, fill with air and become unable to conduct fluid resulting in a wilting of living trees.  The pest is also known to spread blue stain fungi into healthy trees. The nematodes reproduce rapidly (the lifecycle can be completed in as little as four days when conditions are best).  Damage to healthy living trees is rare in California and occurs primarily on non-native pines in landscaping settings.  However, the nematodes have become a major pest causing extensive damage when introduced to Japan and other parts of East Asia.

Recommended Literature

Bergdahl, D.R. 1988. Impact of pine wood nematode in North America: present and future. Journal of Nematology. 20(2):260-265. 

Dwinnell, L.D. 1993. Incidence of the pine wood nematode in green coniferous sawn wood in Oregon and California. USDA Forest Service Research Note SE-367. 4pp.

Dwinnell, L.D. 1997. The pine wood nematode: regulation and mitigation. Annu. Rev. Phytopathol. 35:153-166

Sequoia Pitch Moth

Synanthedon sequoia

More information coming soon

Wood Wasps


More information coming soon

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